Final answer:
The correct direction of energy flow is bidirectional between the system and surroundings, depending on the nature of the reaction, with energy flowing from the system to the surroundings in exothermic reactions and from the surroundings to the system in endothermic reactions.
Step-by-step explanation:
The observed flow of energy in a reaction that involves a system and surroundings can either be from the system to the surroundings or vice versa. When a reaction occurs, energy is not destroyed but is transferred between the system and the surroundings according to the law of conservation of energy. For an exothermic reaction, energy flows from the system to the surroundings, the internal energy of the system decreases, and the reaction is energetically downhill. Conversely, in an endothermic reaction, energy flows from the surroundings to the system, increasing the internal energy of the system, signifying an energetically uphill process. Therefore, the correct directions for energy flow in a reaction are both from the system to the surroundings or from the surroundings to the system depending on the nature of the reaction, making option C) Energy flows bidirectionally between the system and surroundings the correct choice.